Yeah. But even if the IJN was crazy enough to do a conversion (Ise and Hyuga in WW II come to mind and I think I posted something about them in this thread...) they still do not solve their 70% problem. New construction is about as expensive and it gives them more hulls. We can argue that they should have followed a more balanced build and modernize policy and foregone the Yamatos with more logic?
Logic and Japanese strategic planning 1932-1945 don't really mix...
I personally think the
Yamatos, as cool as they were, were wasted tonnage- too slow, too thirsty, too expensive. What, IMO, would have been better, would have been a modernized No. 13 type design (900' x 101' x 32', 47 500t standard, 4 x 2 18"/L50, 30kn). Throw some bulges on it, lengthen it to get the fineness back, pop some Ro-Go turbines in there to make them even faster, and turreted DP secondaries replacing 5.5" LA in casemates and 4.7" AA in single mounts. It's still too big and too thirsty and too expensive, but at least it can keep up with carriers. Either that, or a similarly fast 16" armed ship, like a neo-
Kii or "Fast
Nagato". You could probably build 1 more with the tonnage savings, and stretch every iron doorknob in Tokyo that much farther.
ETA: I also believe that the
Ise and
Fuso classes, both 14" pre-Jutland designs, were really too old to justify the amount of ¥ spent on them, but the IJN was in a bind- with so few capital ships, 12 x 14" x 4 made up a lot of their total firepower, so it's a case of damned if you do (money spent modernizing an obsolete ship is wasted cash), damned if you don't (if you don't spend it, you have a ship that's
more obsolete or no ship at all).
However, there really is no good option for Imperial Japan to fight the kind of war they wanted to fight. Naval strength is built strength, and torpedoing the economy in the name of military buildup inadvertently sabotages that.
Even with Washington ratios, if Japan manages to have Britain, the USA and France allied against them, that's 5 + 5 + 1.75; 11.75 : 3, so off the bat they're outnumbered essentially 4 : 1. Without the Treaty it would be even worse, as Britain, let alone the USA, can out-build Japan easily. With odds like that, the only way to win is not to play, or join a winning team; neither of which 1932-1945 Japan was willing to do.